DC-2762 -- The Decremented Average Ground-Temperature Method for Predicting the Thermal Performance of Underground Walls

At present, the only accurate method for predicting the thermal performance of underground structures is through the use of large computer models and finite difference equations. Due to the prohibitively high cost of setting up and running these computer models, thermal analysis of sub-surface buildings is inaccessible to many prospective users. The existing manual methods for calculating loads on underground buildings provide only rough estimates of thermal performance. All of the existing manual methods ignore the effect of the building on the adjacent ground temperature during an annual cycle, resulting in conservative estimates of the building's heating performance and optimistic estimates of the cooling performance. This paper (1) presents a manual calculation method for accurately predicting the thermal performance of underground walls and (2) gives a table of DECREMENT FACTORS which account for the decreasing thermal loss from underground walls over time.